import java.util.Scanner;

public class Main1 {
    public static int fun(int n) {
        if (n == 1 || n == 2) {
            return 1;
        } else {
            return fun(n - 1) + fun(n - 2);
        }
    }

    public static void main(String[] args) {
        //3  2
        Scanner scanner = new Scanner(System.in);

        int n = scanner.nextInt();
        System.out.println(fun(n));
    }
}
